Once again my adopted home is suffering significant flooding from a stalled tropical system. Parts of the area may have had up to 40 inches of rain in 48 hours or less (Harvey two years ago registered 51 inches, an all time record). Street flooding, Interstates shut down, water rescues, what has become the usual drill here.
Everyone I know is OK, but a friend is stuck at IAH, and the museum I work at has been seriously damaged by water entry from upstairs. We’re going to have quite a mess to deal with when we get there tomorrow, and since the place is pretty much a shoestring operation, there’s a risk it may be unrecoverable. Crap.
It has been a staggering amount of rain east of town. This is the Harris County Flood Warning Service, and through it, you can keep track of rain accumulation and stream heights. https://www.harriscountyfws.org/
Most of the serious rain, from radar estimates, fell just to the east of the warning area, but the east most rain gages are still showing rain accumulations for the last three days in the 30 plus inch range. It’s worse than that east, in places like Winnie and Beaumont. I’ve heard today of 44 inches of rain; the radar estimated near 60 in one spot. Though that spot wasn’t near a rain gage. (EDIT: at this link:Weather Radar | Weather Underground
Scroll down to “total storm accumulation”. Prepare to be surprised.)
The European Meteorological Center’s models, which I’ve mentioned here before, were about the only ones predicting 10-20 inches fro this disturbance. I discounted them in favour of other models that predicted maybe 5-10 inches. Whoops.
It’s been wet. Traffic on the Katy freeway was as light as I’ve ever seen it at rush hour. Lots of cars abandoned in medians, pulled off the street onto curbs, getting towed away, etc… At least I haven’t seen concrete parking lot curbs that floated away, like I have in other floods here.
I prefer not to say, as doing so could affect my anonymity here.
Anyway, two ‘thousand-year’ storms (as one article put it, perhaps hyperbolically) in two years, seems to suggest that the methodology for defining these intervals is a bit out of whack.
And yeah, bad as things were around Houston, the area down around Beaumont seems to have gotten the worst of it, as (IIRC) it did during Harvey.
A news program after Harvey wreaked his havoc explained damages were much greater than ever before because of a questionable deal between developers and politicians which allowed a suburbia to be constructed in a known flood plain.
People who lived in homes which had been unaffected by hurricanes for over 30 years were standing in water up to their unmentionables. The floodplain construction was the obvious culprit. Once you pave over dirt with roads, sidewalks, parking lots, schools and houses, the water has no place to go.
500-year floods are predicted by weather patterns and terrain. You fiddle with terrain and then add global warming, those 500-year floods will be almost an annual occurrence.
I do hope your museum survives with minimal damage. A suggestion if I may: a state agency had sprinklers go off, saturating everything. The historical records were moved while still wet, into freezers at local grocery stores. Later, the records were subjected to essentially freeze drying process. There was a much greater recovery of the records because of this quick thinking.
I don’t believe that is the case.
flood probabilities are always calculated based on historical data. It is a fairly simple calculation. Basically fit all the historical data to a bell curve and look at at the curve for the 50, 100, 500, and 1000 year probabilities. Every time there is a storm, one should recalculate the probabilities. And of course the 50 year flood isn’t predicting that no flood of that size will occur for 50 years-just that there is a given probability that it will occur within 50 years. The prediction is correct if the flood occurs next year. It is only wrong if no flood occurs after 50 years.
Thanks. Fortunately, although there is some water damage to the museum’s main atrium, no artifacts appear to have gotten soaked, so we dodged the bullet this time. It’s an old building and there are some dodgy spots on the roof. One hopes we can get these fixed before the next two-year storm.
This is a very common misperception. “Thousand-year storm” does not mean that such a storm will happen every thousand years. It means that there is a statistical likely-hood of such a storm happening once every thousand years–i.e., there is a 0.1% chance of such a storm happening in any given year.
But the law of large numbers means that improbable things not only can but will happen. Roll the dice often enough, and you find weird coincidences all over the place.
